/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.openjpa.meta;

import java.io.Serializable;
import java.util.Comparator;

/**
 * Order a field.
 *
 * @author Abe White
 */
public interface Order
    extends Serializable {

    /**
     * Token denoting to order by the element value.
     */
    String ELEMENT = "#element";

    /**
     * Return the name of the orderable.
     */
    String getName();

    /**
     * Order direction.
     */
    boolean isAscending();

    /**
     * Return a comparator for ordering by this element, or null if
     * the ordering is done in the datastore.
     */
    Comparator getComparator ();
}
